The invention relates to a method for controlling a communications device which has a main operating unit and a subunit, as well as to a communications device, in particular a submodule of a mobile telecommunications unit, which interchanges data with a main module during time slots which recur at regular intervals.
In the case of a communications device, particularly in the case of a mobile telecommunications unit, whose voltage is supplied with the aid of a battery or a rechargeable battery, it is necessary to keep the power consumption as low as possible in order to ensure that the battery or rechargeable battery operating life is as long as possible and thus that the communications device is ready to operate for as long as possible. To this end, during no-load times, that is to say during times in which no operating functions are required, the communications device is normally changed to standby mode or energy saving mode in which the only circuit devices which are powered are those which are required to set up the full operating capability of the communications device when required.
Fast clock generators are thus normally switched off, while the individual function blocks are still supplied with a controlled voltage in order to keep stored the operating state data which are contained in the individual memories in the function blocks.
In consequence, although the power consumption of the communications device can be reduced considerably in the standby mode, this power saving is, however, not sufficient for communications devices which need to have extremely low power consumption because they can use only very small batteries or rechargeable batteries.
Proceeding from this, the invention is based on the object of providing a method for controlling a communications device, which method permits extremely low power consumption and thus a very long operating life for the voltage source. Furthermore, the object of the invention is to provide a communications device which can be controlled using this method.
According to the invention, this object is achieved by a method for controlling a communications device having a main operating unit and a subunit, in which, after one operating period, operating state data for the main operating unit are stored in a status memory in the subunit and the voltage supply for the main operating unit is switched off in order to change the communications device to an energy saving mode, and in which, after the voltage supply for the main operating unit is switched on, the stored operating state data are transmitted from the status memory to the main operating unit in order to operate the communications device during the following operating period.
The invention thus provides for the operating state data which are required for correct operation of the communications device to be stored in a status memory which is provided for this purpose and is assigned to a subunit, so that the voltage supply for the main operating unit can be switched off completely since only the subunit with the status memory now need be supplied with voltage. After the voltage supply has been switched on for the next operating period, the stored operating-state data are then simply transmitted back to the main operating unit, so that it is fully operational again at the start of the next operating period.
An expedient development of the invention is distinguished by the fact that the voltage supply for the main operating unit is switched on by means of a switch-on signal from the subunit after a respectively predetermined waiting time has elapsed. Both the storage of the operating state data and the monitoring of the switch-on time are thus carried out in the subunit, which can be designed specifically for low power consumption without adversely affecting the operational reliability of the communications device.
It is particularly advantageous for a time indicator to be produced at a time after the voltage supply for the main operating unit has been switched on, in order to define the start time of the following operating period. The time indicator which is provided according to the invention and is produced after the main operating unit has been switched on is intended to occur at a fixed time interval before the start of the following operating period. By detecting the actual time interval between the time indicator and the start of the next operating period, which start can be defined, for example, in a subordinate communications device by means of an external event, such as a received burst, the actual start time for the following operating period can be compared with the assumed start time in order, by lengthening or shortening the energy saving mode, to set the actual interval between the time indicator and the start of the following operating period to the specified interval. However, if the start of an operating period is not dependent on an external event, then the following operating period (in which, for example, transmission operation is carried out) starts after a predetermined time, which is calculated from the time indicator, has elapsed. The time indicator provided according to the invention is thus an absolute time indicator which can be used not only to define the start of operating periods but also to define the duration of the energy saving mode.
In this case, the invention provides in particular that the time interval between the time indicator for the start time and the following operating period is measured by the main operating unit in order to optimize the duration of the effective time for which the main operating unit is switched off in a communications device whose main operating unit operates periodically. Particularly in the case of a submodule in a mobile telecommunications unit, which submodule operates only during specific time slots whose time interval is defined by the communications protocol used or the standard used, this makes it possible for the main operating unit to stay in the energy saving mode for as long as possible between two successive operating periods, that is to say between two time slots.
In this case, it is expedient if the waiting time is predetermined for the subunit as a function of the time interval between the time indicator and the start time of the following operating period by the main operating unit. As a result of the waiting time which defines the switch-on time being determined in the main operating unit, while only the corresponding waiting time supplied from the main operating unit is required in the subunit in order to define the switch-on time, the subunit can be further simplified, as a result of which its power consumption can be reduced further.
In particular, it is possible according to the invention to redefine the waiting time for each operating period.
The switch-on time can be defined particularly easily if the end of the waiting time in the subunit is defined with the aid of a clocked counter, whose running count is compared with a first comparison value which corresponds to the waiting time, that is to say is compared with the waiting time which is transmitted from the main operating unit to the subunit.
A further refinement of the invention provides that the counter is restarted after the waiting time has elapsed, that the running count is compared with a second comparison value, in order to supply to the main operating unit the time indicator which is used to define the start time for the following operating period.
The time indicator, which is produced in this way and is required to define the start time for the following operating period, is in principle at a time interval from the switch-on time for the voltage supply which can be predetermined at any desired fixed value but is normally predetermined as a value fixed by the circuit design, and corresponds to the end of the waiting time. Adaptation of the waiting time thus allows the switch-on time for the voltage supply for the main operating unit to be at a predetermined time which, on the one hand, is sufficiently late that the time between the two operating periods is used in an optimum manner for the energy saving mode, but on the other hand is sufficiently early that the main operating unit has sufficient time to ensure stable operation of its fast clock generator and to recover the operating state data from the status memory for the following operating period.
The method according to the invention expediently provides for the counter to be started with the aid of software reset command which is supplied from the main operating unit. This makes it possible to reduce the number of signal lines between the main operating unit and the subunit in a circuit for carrying out the method according to the invention, since one data line can be used for the reset command.
In order to keep the duration of the process of switching the main operating unit on and off as short as possible so that the time period between two successive operating periods can be utilized even better, a particularly preferred refinement of the invention provides that a clock signal is transmitted from the main operating unit to the subunit in order to store the operating state data for the main operating unit in the status memory in the subunit and in order to read the operating state data from the status memory. Thus, according to the invention, the fast clock for the main operating unit is used for storing and reading the operating state data, so that neither the switching-off process nor the switching-on process is unnecessarily long drawn out.
The method according to the invention can expediently be used if the operating periods of the main operating unit are matched to time slots which recur at regular intervals, during which the main operating unit interchanges data with a higher-level communications device, that is to say, for example, if the main operating unit of a submodule of a mobile telecommunications unit communicates with its main module via a radio interface.
Another development of the invention is distinguished by the fact that the respectively following operating period is started by an external event, which occurs at regular intervals at least during a time period which comprises a plurality of operating periods, in particular by a burst which can be received by the main operating unit, that is to say by a signal bundle that is used in the time-division multiplex, multiple-access method.
The method according to the invention can also be used, however, particularly advantageously in the case of higher-level communications devices which start the operating period without being dependent on external events. In this case, the invention provides for operating periods to be started in each case as soon as their start time has been defined with the aid of the time indicator.
A particularly preferred refinement of the invention is distinguished by the fact that the main operating unit produces a switch-on hold signal in order to maintain its voltage supply after switching on during the operating period and to switch itself off after the end of the operating period.
A communications device according to the invention, in particular a submodule of a mobile telecommunications unit, which submodule interchanges data with a main module during time slots which recur at regular intervals, has a main operating unit for carrying out assigned functions, and a subunit which has a status memory for operating state data for the main operating unit, and a timing circuit which controls the voltage supply for the main operating unit.
In this case, it is particularly advantageous if the timing circuit has a clocked counter whose counter output is connected to one input of a comparison circuit, which compares the count from the counter with a comparison value which is defined by the main operating unit, in order to produce a switch-on signal for the voltage supply for the main operating unit, one output of the comparison circuit being applied to a hold circuit which emits the switch-on signal for a time period.
In this case, it is expedient if the timing circuit has a second comparison circuit, which compares the count with a second comparison value, in order to supply to the main operating unit an output signal which provides a time indicator for defining the start time of the following operating period for the main operating unit.
An expedient refinement of the invention provides that the output signal of the second comparison circuit is supplied to the main operating unit via a gate circuit as an indicator signal, which gate circuit is controlled by an enable signal, which indicates the type of switch-on process. In this way, the indicator signal which is required to set the waiting time can be used in order to transmit further operating state information from the subunit to the main operating unit, without any additional data or signal line being required for this purpose. In particular, the further operating state information may comprise information about whether the main operating unit is being switched on from a completely switched-off state or from the energy saving mode.
In order to reduce the power consumption of the communications device further, the invention provides that the counter in the subunit is clocked by a clock generator which is integrated in a further electronic device with which the communications device is associated. The use of an external clock generator, which is provided in a further electronic device associated with the communications device, allows the number of loads which are activated in the subunit during the energy saving mode to be reduced further. In particular, the subunit does not require a voltage regulator, so that a considerable reduction in the power consumption is achieved by omitting this load, which is normally the largest load in the energy saving mode.
Furthermore, in this case, the subunit can be arranged separately from the main operating unit in another electronic device, so that the voltage source for the further communications device can be used for the voltage supply for the subunit. This further reduces the load on the battery or the rechargeable battery in the communications device.
For fast storage and reading of operating state data, it is expedient if a bus having a clock signal line and a data line is provided for data interchange between the main operating unit and the subunit, so that a fast memory and read clock, respectively, can be transmitted to the subunit in order to store and read the operating state data in and from, respectively, the status memory.